Kenneth Chesky

Computer diagnosis of electrocardiograms. IV. A computer program for contour analysis with clinical results of rhythm and contour interpretation

Abstract The logic for the contour analysis programs and the results of a comparison of computer and physician diagnosis for over two thousand cases are described. A detailed breakdown of the patient population and nature of the errors made by the program is given. The effectiveness of the program as a screening tool is also considered.

The Two-Step Exercise Electrocardiogram A Double-Blind Evaluation of Its Use in the Diagnosis of Angina Pectoris

A double-blind study was made to evaluate the two-step exercise electrocardiographic test (Master) as a means of differentiating between anginal and nonanginal chest pain in 100 consecutive patients. A high percentage of false-positive results in nonanginal cases and a number of false negatives in anginal cases greatly impaired the usefulness of the test for this purpose. When Masters criterion of an ST depression of 0.5 mm. or more was employed, there were 39 per cent false positives and 12 per cent false negatives. Stricter criteria progressively diminished the number of false positives, but resulted in increasing numbers of false negatives. Even if 1 mm. or more of ST depression was required, there were 8 per cent false positives and 43 per cent false negatives. There were no false positives only when the ST segment was depressed 2 mm. or more. Although an ischemic type of ST depression may be more significant for angina pectoris than the J type, in our series ischemic ST depressions also occurred more frequently than the J type in false-positive tests in nonanginal patients. The new criteria of Master and Rosenfeld were not more satisfactory than the previous criteria recommended. There are relatively few cases in which an objective two-step test is necessary to aid in the differentiation of anginal and nonanginal pain, since an unequivocal diagnosis of angina pectoris or nonanginal pain was made in 86 per cent of cases independently by at least two observers, on the basis of a single interview, and since this percentage could undoubtedly have been increased by further interviews concerning the effect of effort and of nitroglycerin. Insofar as confirmation of a clinical diagnosis of angina pectoris by an objective exercise test is desirable, an ST-segment depression of at least 1 mm. usually offers such confirmation. However, this degree of ST-segment depression is often absent in unequivocal cases of angina pectoris and conversely may be occasionally present in patients with nonanginal pain.

Clinical evaluation of the ballistocardiogram: II. Heart disease—Hypertension, angina pectoris, and myocardial infarction

Abstract 1. 1. Analysis of ballistocardiographic tracings has been made in a group of 135 subjects with known cardiac disease. 2. 2. In the patients with essential hypertension and hypertensive heart disease, only 2 were found to have a completely normal ballistocardiogram at rest. 3. 3. Seventy-five per cent of the angina patients with negative resting electrocardiograms (and positive exercise electrocardiogram tests) showed abnormal ballistocardiographic patterns at rest. Of 5 angina patients with normal resting ballistocardiograms, the ballistocardiogram in 4 became abnormal only after exercise. 4. 4. The ballistocardiogram was abnormal at rest in over 92 per cent of the patients with previous myocardial infarction. 5. 5. Preliminary confirmatory evidence of the valuable aid of the ballistocardiogram in everyday clinical practice is presented.

Clinical evaluation of the ballistocardiogram

Abstract 1. 1. The ballistocardiogram, as recorded by the photocell displacement apparatus (modified after Dock), was investigated in a consecutive group of eighty normal control subjects. 2. 2. In the series of normal subjects, the ballistocardiogram was found to be normal at rest in seventy, abnormal in seven, and borderline in three. The significance of these findings has been discussed. 3. 3. Of fifty-three normal controls with normal resting ballistocardiograms who were exercised, the ballistocardiogram in forty-eight remained normal after the double “2-step” test. A careful follow-up study of the normal subjects with abnormal ballistocardiograms will be made in order to determine the clinical implication of these findings. 4. 4. The unhinged photocell displacement ballistocardiogram apparatus was employed with a simple method for simultaneous recording of the electrocardiogram with the commonly employed single-channel cardiographic machines.

The dual displacement and velocity ballistocardiograph apparatus

Abstract 1. 1. A dual ballistocardiograph apparatus for recording simultaneous or successive displacement (photoelectric) and velocity (electromagnetic) ballistocardiograms is described. 2. 2. The technique for establishing reproducible standardized conditions for ballistocardiographic tracings is described; work is in progress on standardization of recording equipment. 3. 3. A respiratory filter (for photoelectric tracings) as well as simultaneous electrocardiograms may be utilized by a simple switch arrangement. 4. 4. Lateral and anteroposterior ballistocardiographic tracings, as well as the customary longitudinal ones, may be recorded with the new apparatus.

The Ballistocardiogram in Myocardial Infarction: A Study of One Hundred Cases

In the presence of previous myocardial infarction, the direct ballistocardiogram is abnormal in approximately 80 per cent of the cases. Following the coronary occlusion, a normal ballistocardiogram is relatively rare in patients with angina pectoris as compared with those who are asymptomatic. There is no correlation between the ballistocardiographic patterns and the persistence of electrocardiographic evidence of myocardial infarction. The prognostic significance of the ballistic findings reported will be determined by long-term follow-up studies.

The ballistocardiogram in congenital heart disease

Abstract 1. 1. The ballistocardiogram in varied congenital cardiac malformations has been presented and discussed. 2. 2. Short K waves are uniformly present in coarctation of the aorta, but this finding is not specific since patients with interatrial septal defect, Eisenmenger complex, and patent ductus arteriosus may display similar findings. 3. 3. Pulmonic stenosis does not produce low amplitude abnormal ballistocardiographic patterns, as has been reported. The record often is entirely normal and actually may be characterized by increased voltage. 4. 4. Tricuspid atresia produces prominent H waves. 5. 5. The other congenital cardiac malformations studied do not produce specific abnormalities. 6. 6. In our opinion the ballistocardiogram has little practical value in the study of congenital cardiac malformations.

The Extremity and Circumferential Chest Lead Electrocardiogram in Induced Acute Coronary Insufficiency

The extremity and circumferential chest lead electrocardiogram (twenty-two leads) was studied in 8 patients with generalized coronary insufficiency induced by exercise. Over the right chest, posteriorly and laterally, there was noted RS-T elevation similar to but less pronounced than that occurring in lead aVR. These leads probably represent true or mixed cavity potentials. Standard leads revealed more marked RS-T alterations after exercise than did aV leads. In the left anterior chest leads, the greatest RS-T depression occurred in the left unipolar precordial leads representing the maximal voltage of the R wave—usually V4 or V5. The practical application of these findings is discussed in relation to routine two step exercise tests.

Unipolar Bronchial Electrocardiographic Exploration of the Heart in Man A Preliminary Report

The method for exploring cardiac potentials through the bronchial tree is described in detail. It consists of obtaining unipolar bronchial leads by inserting a thin No. 4 French catheter into the secondary branches of the bronchial tree as near as possible to the surface of the heart. By this method, electrocardiograms can be obtained on the right side which resemble right auricular endocardiograms. On the left side, left ventricular epicardial and cavity potentials are recorded and these are similar to direct left ventricular surface leads, left intraventricular cavity potentials and esophageal leads at the same level. No arrhythmias or serious reactions occurred during or after this procedure. Preliminary findings in 8 cases are discussed in detail.